He grins and crouches down. He gives Jack the coin and shows him how to hold it.

Okay so, first you hold it like this... then you hide it in your palm. Like this.

He shows Jack how to change the way he holds it, so the coin 'disappears.'

Then when you take it from someone's ear - or wherever - you slide it back into your fingers again. It takes practice, but then it gets easy.